I'm not learning physics in English, so terminolgy might be wrong. 1. The problem statement, all variables and given/known data How does this circuit function? Where do the electricty flow? 2. Relevant equations No equations 3. The attempt at a solution Not sure what to put here? My question is basically how it work. As far as I know, the circuit starts at the positive side of the power source, and "splits" by some part of the electrons going to the LDR1 and the other part continues going to the right, and continues branching everytime it can. But how does the light sensitivity thing work? Where do the electricity go for it to start the siren/buzzer? There is nothing near LDR1, so what activates it and what makes it stop, if there is no resistor or anything there to stop it? Does this make sense? New to physics.